Point-contact spectroscopy of MgB2

Abstract

Point-contact spectroscopy measurements on magnesium diboride reveal the existence of two superconducting energy gaps closing at the same transition temperature in line with the multiband model of superconductivity. The sizes of the two gaps (${\Delta }_{\pi }$ = 2.8 meV and ${\Delta }_{\sigma }$ = 6.5-7 meV) are respectively smaller and larger than the expected weak coupling value of the one-gap superconductor. The smaller gap is rapidly filled by a small magnetic field of about 1-2 Tesla much lower than the real upper critical field $H_{c2}$. The larger gap is closed at the anisotropic $H_{c2}$. Above the gap energies reproducible non-linearities are observed at the characteristic phonon energies of MgB${}_2$.

14 pages incl. 8 eps figures

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• Advances in point-contact spectroscopy: two-band superconductor MgB2 (A review)
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• Single-gap two-band superconductivity well above the Pauli limit in non-centrosymmetric TaIr${}_2$B${}_2$
• Exploring unconventional superconductivity in PdTe via Point Contact Spectroscopy